When Christina Aguilera and Cee Lo Green announced last fall that they’d sit out the current season of “The Voice,” which premiered Monday night on NBC with Shakira and Usher as the new judges, both singers said they planned to spend more time focusing on music.

Yet three months after they vacated their red-pleather judges’ chairs, the two don’t have much to show for it: Aguilera’s “Lotus” album bombed (despite an awesomely freaky performance at the American Music Awards), while Green is starring in a coolly received production at Planet Hollywood in Las Vegas. It’s called “Cee Lo Green Is Loberace.”

Their achievements appear especially puny compared to those of the “Voice” judges who stayed on. Adam Levine’s Maroon 5 has two songs on Billboard’s Hot 100 singles chart right now, and this month the band sold out a concert at L.A.’s Staples Center. Blake Shelton currently sits atop two of Billboard’s country charts with “Sure Be Cool if You Did,” the lead single from his new album, “Based on a True Story ...”

Maybe brand synergy matters more these days than artistic dedication? Well, duh.

Country music’s most relaxed superstar, Shelton barely breaks a sweat throughout “Based on a True Story ...,” which like 2011’s “Red River Blue” sounds as if it were recorded in the rear lounge of a private jet zooming back and forth between Nashville and L.A.

In “Ten Times Crazier,” his laid-back delivery belies words about how over the moon he is for a lady friend, while “Boys ‘Round Here” streamlines country’s obsession with small-town signifiers by doing away with the complexities of a plot. It’s basically a string of unconnected SEO keywords: ice-cold beer, Dixie Crystals sugar, “Chew tobacco / Chew tobacco / Chew tobacco / Spit.”

And “Sure Be Cool if You Did”? Here’s a song in which the narrator lays out an elaborate meet-cute at a bar (complete with a “pretty pink lemonade shooter”), then decides it’s no big deal if she’s just not that into him. “Baby, it’s your call / No pressure at all,” he sings, a slacker masquerading as a gentleman.

Yet if Shelton’s investment in his material here seems about as minimal as possible, it’s a testament to his considerable charm that “Based on a True Story ...” never feels like a con. With its easy rhymes and hummable choruses, the album doesn’t ask the listener to work any harder than Shelton himself is prepared to work.

Indeed, its best tunes are the ones in which you can hear Shelton cracking himself up, as in “Doin’ What She Likes,” which depicts his marriage to fellow country singer Miranda Lambert with this hilariously lazy couplet: “She likes it when I bring home fresh fajitas / And mix up a pitcher of margaritas.” (“It’s a pretty light album,” he recently admitted to USA Today.)

In “Country on the Radio,” he positions his soft thinking as a component of roots-music tradition, asking, “You ever wonder why country songs say the same ol’ thing?” over an easygoing midtempo groove. The song actually declines to unlock that mystery, but that’s probably just as well. With Shelton, it’s not the journey that matters, but the destination.